Prof Kevin Sullivan

Research interests

Centromere replication: epigenetic chromosome inheritance

Mitotic checkpoints, apoptosis and cancer chemotherapeutics

Quantitative microscopy and phenotypic analysis of cells

Research overview

Successful passage of cellular generation requires the replication of the chromosomes and their segregation into new daughter cells. Centromeres are the chromosomal sites that direct chromosome segregation.

Our lab is focused on understanding the molecular organization of centromeric chromatin. Centromeres are unusual in that the functional identity of the locus is not determined by DNA, but by the proteins associated with them. Examination of the assembly of a chromatin complex comprised of proteins CENP-T/W/S/X has identified a distinctive chromatin assembly pathway active after DNA replication that is required for kinetochore formation. (Fig 1).

Figure 1. The CENP-T/W/S/X particle (top left) was shown to assemble in vivo in late S/G2 (top right) leading to the hypothesis that a novel chromatin assembly pathway is active in G2, required for kinetochore assembly.

Efforts are currently focused on mapping centromeric chromatin using a novel equine cell system developed by collaborator Elena Giulotto at the University of Pavia. Analysis of Equus asinus, the domestic donkey, has identified a set of centromeres that are formed on unique genomic DNA sequence rather than repetitive satellite DNA. These centromeres open an avenue for application of ChIP-Seq methods for dissection of chromatin structure. (Figure 2) We are currently investigating the nucleosomal organization of the centromere and identifying the location of inner centromere components. The long range goal of these experiments is to establish a high resolution molecular map of the centromeric chromatin fiber and its critical components under different physiological conditions in the cell cycle.

Figure 2. Equus asinus, the domestic donkey, contains several centromeres established on satellite-free stretches of genomic DNA, detectable by ChIP-Seq analysis with CENP-A antibodies (top). Analysis of this ensemble will provide new insight into the architecture and regulation of the centromeric chromatin fiber. Shown at bottom, centromeres share very similar CENP-A abundance despite ~5 fold differences in their genomic footprints.